Vacuum cleaners include a variety of types ranging from heavy duty shop-type vacuum cleaners used in, for instance, basements, work rooms, and garages, and canisters and uprights used for medium to heavy-duty cleaning floors and floor coverings, furniture, and draperies, to the so-called stick-type vacuum cleaners which are used for light-duty dirt pick-up such as kitchen floors, and some light carpet cleaning.
Typically in conventional vacuum cleaners the air in the cleaner casing is discharged by a motor fan, so that the pressure in the casing is lower than atmospheric pressure. A high speed air stream is formed by this air pressure differential, causing the corrupt air including dust to be inhaled through a dust in-let plate and flexible hose with an air suction hole, and passed to a filter unit with a solid filter of paper or cloth. As the fine pores of the air filter are clogged by dust, the intake air power of the machine declines rapidly. Most of the large particles of dust are intercepted by the filter but micro particles are passed through the filter with the air and returned to diffuse back into the room. Thus, the room air becomes more turbid and harmful to health.